package com.baobaotao.basic;

public class SequenceNumber {
     
        //①通过匿名内部类覆盖ThreadLocal的initialValue()方法，指定初始值
	private static ThreadLocal<Integer> seqNum = new ThreadLocal<Integer>(){
		public Integer initialValue(){
			return 0;
		}
	};
     
        //②获取下一个序列值
	public int getNextNum(){
		seqNum.set(seqNum.get()+1);
		return seqNum.get();
	}
	
	public static void main(String[ ] args) 
	{
          SequenceNumber sn = new SequenceNumber();
         
         //③ 3个线程共享sn，各自产生序列号
         TestClient t1 = new TestClient(sn);  
         TestClient t2 = new TestClient(sn);
         TestClient t3 = new TestClient(sn);
         t1.start();
         t2.start();
         t3.start();
	}	
	private static class TestClient extends Thread
	{
		private SequenceNumber sn;
		public TestClient(SequenceNumber sn) {
			this.sn = sn;
		}
		public void run()
		{
                        //④每个线程打出3个序列值
			for (int i = 0; i < 3; i++) {
			System.out.println("thread["+Thread.currentThread().getName()+
"] sn["+sn.getNextNum()+"]");
			}
		}
	}
}